1. Field of the Invention
The present invention relates to a solid-state imaging apparatus and a digital camera, and more particularly, to a solid-state imaging apparatus and a digital camera which achieve superior white balance when imaging a subject under a plurality of types of light sources, to thus produce an image with little color fogging.
2. Description of the Related Art
In a digital camera, such as a digital still camera (including one embedded in a portable cellular phone) or a digital video camera, a solid-state imaging device, such as a CCD or a CMOS image sensor, images a subject, corrects white balance of the thus-obtained image data in accordance with the type of illumination light radiated on the subject, and outputs the corrected white balance.
Previously-expected light sources include various typical light sources such as sun light (a D65 light source, a D75 light source or the like), a normal type white fluorescent lamp (an F6 light source), a three-band fluorescent lamp (including an F10 light source, an F11 light source, an F12 light source, or the like), and flash light. When automatically performing correction of white balance, the digital camera analyzes imaged image data and determines the type of the light source, to thus use correction values conforming to the type of the light source.
However, when photographing is performed, there may be a case where a subject is illuminated by only one type of light source and a case where there is photographed a scene of a subject being illuminated by a plurality of types of light sources. For instance, there is a case where an indoor scene is photographed with sunlight streaming through panes and in the interior of a room illuminated by a fluorescent lamp.
When image data—which have been imaged by means of photographing a subject illuminated by a plurality of types of light sources—are subjected to white balance correction, only one principal type of light source has hitherto been determined, and the entire image is corrected on the basis of the type of that light source. A remaining portion of the image outside the principal subject; that is, a portion of the image chiefly illuminated by other types of light sources, is susceptible to color fogging, to thus assume a strong yellowish or greenish tinge. This raises a problem of deterioration of color reproducibility (particularly reproducibility of gray or flesh color).
To solve the problem, the related-art technique described in, e.g., paragraph number [0026] of JP-A-8-340542 (corresponding to U.S. Pat. No. 5,808,681), proposes the following processing. Specifically, when a principal subject is photographed with a flash within a room illuminated by an F6 light source, the amount of influence of flash light is determined for each image area of a photographed image from image data obtained by a solid-state imaging device before emission of the flash and image data obtained by the solid-state imaging device after emission of the flash. In accordance with the amount of influence, the amount of correction on white balance is determined on a per-image-region basis, thereby generating an image having a superior white balance over the entirety thereof.
However, the related-art technique of JP-A-8-340542 is directed solely toward the case of emission of flash light and is configured such that two image data sets; that is, image data obtained before emission of a flash and image data obtained after emission of the flash, must be used.
For this reason, the technique described in JP-A-8-340542 cannot be applied to correction of white balance achieved when a subject under a plurality of types of light sources other than flash light has been photographed. The reason for this is that, when an indoor scene with sunlight streaming in through panes of a room illuminated with fluorescent lamps is photographed, only a single image data is obtained and image data to be obtained before being irradiated with sunlight or fluorescent lamps cannot be acquired.